Two very long parallel plates are maintained at uniform temperatures of $T_1=850K$ and $T_2=550K.$ The respective emissivity are $0\mathrm{.}6$ and $0\mathrm{.}8.$ Between the two plates, an absorbing and emitting gas having an absorption coefficient $0\mathrm{.}08m^{-1}$ at a uniform temperature $T_g=400K$ flows. The spacing between the plates, $L=1\mathrm{.}2m.$ Neglecting any convection between the gas and the plates, compute the net radiative heat flux at the two walls under the following conditions:

a$.$ Considering gas as non$-$participating medium

b$.$ Considering gas as participatory.